What does it mean when a girl does this?

What does it mean if you are walking towards a girl in the halls you make eye contact and after a few seconds she smiles first at you? Could it just be to avoid any awkwardness of the situation or could she possibly like me? Also we are seniors in high school and she is shy. Also this has happened multiple times. She's also at her locker when this happens so she'll look at me and smile, look back at her locker again as she's getting her stuff and she won't say anything to me even though i'm right beside her and if I do say something she talks fairly quietly.